Electron discharge device



Aug. 12, 1941. A. v. HAEFF ELECTRON DISCHARGE DEVICE Filed March 9, 19403 Sheets-Sheet 1 ELECTRON BEAM ELECTRON BEAM ELECTRON BEAM fl 4m 0111(AM EMA M 06 0! N 0 mu Ma Q,

.n llllll lllllllllllllllllllllllll 1 HEN/ml /8EAM INVENTOR. ANDREW MHAEFF By A vfikmkam 0 ATTORNEY.

Aug. 12 1941. A. v. HAEFF 2,252,565

ELECTRON DISCHARGE DEVICE Filed March 9, 1940 3 Sheets-Sheet 2 INVENTOR.ANDREW 1/. HAEFF ATTORNEY.

Aug. 12, 19411 A. v. HAEFF ELECTRON DISCHARGE DEVICE Filed March 9, 19403 Sheets-Sheet 3 T WN R. l a 2 5 25 MM h J a k A If? I T 1 #1 Q l/ f; aL

my u MA m EH c 0 W n 1 W m N A Patented Aug. 12, 1941 OFICE ELECTRONDISCHARGE DEVICE Andrew V. Haeff, East Orange, N. 3., assignor to RadioCorporation of America, a corporation of Delaware Application March 9,1940, Serial No. 323,071

Claims.

My invention relates to electron discharge devices, more particularly tosuch devices utilizing a plurality of electron beams.

One of the difficulties encountered with tubes utilizing electron beamshas been the eifeot of space charge. Space charge causes the lowering ofspace potential between the cathode and anode, thus setting an upperlimit to the perveance of the electrode system and changing the electronvelocity distribution over the cross section of the beam. Space chargemay also give rise to hysteresis eifects.

It is therefore the principal object of my invention to provide anelectron discharge device utilizing an electron beam or beams in Whichthe effects of space charge are substantially reduced or eliminated.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims, but theinvention itself will best be understood by reference to the followingdescription taken in connection with the accompanying drawings in whichFigure 1 is a longitudinal section diagrammatically showing an electrondischarge device employing a beam, Figure 2 is a section taken along theline 2--2 of Figure 1, Figure 3 is a diagram representing the spacepotential for difierent current densities of an electron beam passingthrough the tube shown in Figure 1, Figures 4, 5, 6 and 8 are transversesections of tubular electrodes and beams extending through saidelectrodes, Figures 7 and 9 are diagrams showing' space charge potentialtransverse 0f the tubular members shown in Figures 6 and 8,

Figure 10 is a side elevation partially in section of a beam tubeemploying the principles of my invention, Figure 11 is a transversesection of the tube shown in Figure 10, Figure 12 is a longitudinalsection of another form of beam tube made according to my invention,Figure 13 is a longitudinal side view of the tube shown in Figure 12,and Figure 14 is a section taken along the line l4l4 of Figure 13.

To illustrate the problem and solution provided by my inventionreference is had to Figures 1 to 9 inclusive.

In the electrode arrangement shown in Figure 1 the cathode l0 supplies abeam of electrons, which is collected by the anode or collector II. Thebeam may be formed by electrode 12 which may be at a positive ornegative potential with respect to the cathode l0 and may, if desired,be modulated by the electrode I2 before passing through shieldingelectrode !3, the sheath electrode l4 and the shielding electrode 15.This sheath electrode 14 is preferably maintained at a positivepotential with respect to the cathode. The position of the beam withrespect to the sheath M is shown in Figure 2. As shown in Figure 3 withno current flowing through the sheath the space potential inside thesheath is uniform as indicated by the line a. As the beam current isincreased the spacepotential will decrease. The distribution of thespace potential across the beam for different values of the in jectedcurrent is shown by lines I), '0 audit. Curve d represents thedistribution for the maximum current flow. If the injected current isincreased above this maximum current the space potential will dropdiscontinuously to zero at the center of the beam at some pointalong'the length of the beam, thus forming a virtual cathode at thatpoint. Partial electron reflection from the virtual cathode back to thecathode will result in a decrease of the collected current with anyfurther increase in the injected current. The magnitude of the maximumcurrent that can be passed through the sheath electrode depends upon thetransverse dimensions and shape of the beam and the sheath electrode,upon the current distributions over the cross section of the beam and isproportional to the 3/2 power of potential of the sheath electrode. Ifthe sheath electrode is' long compared to" its opening and the beamcross section is kept con-' stant by proper focusing, such as by amagnetic field in the direction of electron flow, then the maximumcurrent does not depend 'upon the length of the beam and upon thepotential of the end electrodes. The perveance G511 of the sheathelectrode may be defined as the ratio of maximum current to the 3/2power of sheath potential (Vsh), that is max V s/z In general, theperveance of the tube can be quired when the clearance between the beamand the sheath electrode is made smaller.

In accordance with my invention I provide an eifective method ofminimizing the eifects of space charge. In Figure 6 is shown a sheathelectrode of rectangular tubular cross section with a centrallypositioned beam of rectangular cross section. The space potential isindicated in Figure 7. In accordance with my invention I subdivide thesheath into a plurality of closely adjacent cellular passageways bylongitudinal partitions so that each of the passages or cells passesonly a fraction of the total current. The space potential is then thatshown in Figure 9 and it will be observed that the depression of thespace potential is only slight. Because the perveance of themulti-cellular sheath electrode is proportional to the square of thenumber of cells for the same total cross section, the potentialdistribution for the same total current is more uniform throughout thecross section for the multi-cellular electrode. At the same time, therequired focusing field is approximately the same for the two cases,because the reduction in the space charge field compensates for thereduced spacing between the beam and the sheath.

My invention can be applied to the so-called velocity modulation type ofhigh frequency beam tube to provide a tube of this kind having a highperveance, which characteristic is particularly desirable with this typeof tube. In this type of tube the negative conductance when the tube isused as an oscillator or the transconductance when used as an amplifieris proportional to the ratio of beam current to beam potential. Also, itis desirable to reduce the spread of electron velocities over the crosssection of the beam because of the desirability of obtaining uniformelectron transit time. Both of these requirements necessitate thereduction of space charge eifects which can be accomplished best by theuse of multi cellular structures according to my invention. Anotherimportant advantage of multi-cellular structures in tubes having aplurality of electrodes in succession and used at high frequency is thatbecause of the closely spaced partitions of the cells, the penetrationof the potential field of one electrode into the adjacent electrodeseparated by a small gap is considerably reduced. This reduces theeffective length of the gap and hence the electron transit time acrossit with a consequently more effective interaction between the electronstream and the active electrodes.

In Figures 10 and 11 is shown a socalled pushpull delay-grid oscillatormaking use of velocity modulation in which my invention employing themulti-cellular structure is used. The cathode may comprise two or moreindependently supported indirectly heated cathode elements, each ofwhich supplies oppositely disposed streams of electrons. These electronstreams are formed into a plurality of beams which may be focused byelectrode 2| to pass through the accelerating electrodes 22 havingcellular passages registering with each of the electron beams. Themagnitude of the average current may be controlled by the flat typespace charge grid 2|, to which a modulating voltage may or may not beapplied. The accelerating electrodes 22 also serve to screen the cathode20 from the radio frequency part of the tube. The electrons arecollected by collector 24 after passing through output electrodes 23.All of the electrodes are mounted within evacuated envelope 25 andsupported from the stem 25. The multi-cellular electrodes 23 may, asbest shown in Figure 10, be connected to an oscillating circuit 28 in apush-pull arrangement, the positive voltage being supplied through themidpoint of the circuit from voltage source 21. The magnets 26-26 supplythe magnetidfield parallel to the electron beams for maintaining thebeams focused.

The electron streams are velocity modulated in the gaps between theelectrodes 22 and 23; that is, electrons approaching the electrodes 23across the gap between electrodes 22 and 23 at the time that the voltageon these electrodes is negative with respect to the average voltage areslowed down whereas electrons approaching this electrode when thepotential on the electrode is positive are accelerated. Thus theelectrons after passin the gap are moving at diiferent speeds throughthe electrode 23. Inside the output electrodes 23 the slow electrons areovertaken by the fast electrons so that the electrons leave electrode 23in more or less well defined groups and in so doing the velocitymodulated stream is converted into a current modulated stream so that asthe electrons emerge from the electrodes 23 and flow across the gapbetween it and the collector 24 they induce a radio frequency voltageand current in electrode 23 and the oscillating circuit 28 connected tothese two electrodes purely by the inductive action of the electronstream on the two electrodes 23. Energy is absorbed from the electronsas they leave the electrode 23 if the potential on the electrodes 23 ispositive. The electrons absorb energy from these electrodes andconnected circuit if the electrodes are negative as the electrons leavethe electrodes 23. The length of the electrode 23 and the associatedcircuit elements are such however that there is a net transfer of energyfrom the modulated electron stream to the output electrodes 23 and theirassociated circuit. Thus the electrons are decelerated in the gapsbetween these output electrodes 23 and the collector electrode 24. Theuse of the multicellular electrodes in tubes of this type isadvantageous for the reasons pointed out above.

Another example of an electron discharge device made according to myinvention is shown in Figures 12 to 14 inclusive, in which a velocitymodulated type of amplifier tube is shown. An envelope 35 is provided atone end with a circular re-entrant portion 36 through which lead wiresextend to the various electrodes within the envelope. The electrodes,which as best shown in Figure 13 as supported between insulating spacingmembers 31 and 38, are so arranged as to provide a push-pull modulatedtube. The cathode 39 is provided with a plurality of coextensiveemitting sections indirectly heated and registering with longitudinalslots in the beam forming grid 46, the two portions of the cathode 39being connected to different lead-in wires. A cellular type tubularelectrode 4| is next provided for accelerating the beams of electronsdirected through the cellular portions of this electrode. This isfollowed by the cellular type input control or modulating electrodecomprising the portions 42 and 42 which are electrically separated fromeach other and which register with the cellular passages through theaccelerating electrode ll. The electron transit time through themodulating or input electrodes may be made approximately equal to a halfperiod of oscillation. The six-cell drift electrode 43 provides a spacein which the fast electrons of the velocity modulated beams tend tocatch up with the slow electrons so that upon emerging from the driftelectrode 43 the electron stream becomes current modulated and inducescurrent in the pushpull ouput electrodes 44 and 44". These outputelectrodes are provided with cellular passageways registering with thecellular passages in the drift space electrode. They are in turnfollowed by the electrode 45 having a plurality of cellular passagesregistering with the other passages and a collector electrode 46 whichis suitably supported on the re-entrant stem 4! of the envelope. Thepush-pull input circuit is connected between the control electrodes 42and 42' biasing being supplied by the biasing battery 52 connected tothe mid-point of the input circuit 49. The grid electrode 40 is suitablyconnected to the voltage source 52* to provide a biasing potential.Accelerating electrode 4|, the drift tube 43 and the electrode 45 areconnected to source 5| for proper bias. The output electrodes 44 and 44are connected to the opposite sides of the output circuit 50 to whichvoltage is applied to the mid-point by proper connection to the voltagesource 52. The leads to the input and output electrodes may be providedas shown in Figure 13 at 421 and 441. A magnetic field for focusingpurposes is provided by the solenoid 54 surrounding the tube envelope.This tube operates in substantially the same manner as that shown inFigures and 11, except that the three important functions, namely,velocity, modulation, conversion of velocity modulation into currentmodulation and extraction of energy from the electrons are performed bythree separate electrodes, 42, 43, 44, so that the tube can be used foramplification as well as for generation of radio frequency energy.

While I have indicated the preferred embodiments ofmy invention of whichI am now aware and have also indicated only one specific application forwhich my invention may be employed, it will be apparent that myinvention is by no means limited to the exact forms illustrated or theuse indicated, but that many variations may be made in the particularstructure used and the purpose for which it is employed withoutdeparting from the scope of my invention as set forth in the appendedclaims.

What I claim as new is:

1. An electron discharge device having means for supplying electrons,means for forming said electrons into a plurality of closely adjacentparallel beams, electrode means adapted to receive an alternatingpotential for simultaneously controlling said plurality of beams, otherelectrode means including a tubular electrode having a plurality ofelectrically connected partitions extending longitudinally of saidelectrode for providing a plurality of closely adjacent parallelcellular passages extending therethrough I and through which saidelectron beams are directed, each of said beams substantially fillingits respective cellular passage whereby said beams are closely adjacenteach other but have no electrical effect on'each other, and electrodemeans for receiving said beams.

2. An electron discharge device having a cathode for supplyingelectrons, means for forming said electrons into a plurality of closelyadjacent parallel beams and for simultaneously controlling saidplurality of beams, means including a tubular electrode havingaplurality of electrically connected partitions extendinglongitudinallyof said electrode for providing a plurality of closely adjacent parallelcellular passages extending therethrough and through which said electronbeams are directed, each of said beams substantially filling itsrespective cellular passage whereby said beams are closely adjacent eachother but have no electrical'effect on each other and a second tubularelectrode adjacent said first and provided with a plurality ofelectrically connected partitions extending longitudinally of saidelectrode for providing a plurality of closely adjacent parallelcellular passages extending therethrough and registering with thecellular passages in the first tubular electrode, and electrode meansfor receiving said electron beams after passage through said tubularelectrodes.

3. An electron discharge device having a cathode for supplyingelectrons, means for forming said electrons into a plurality of closelyadjacent parallel beams, electrode means for receiving said electrons,electrode means positioned between the cathode and receiving meansadapted to receive an alternating potential for simultaneouslycontrolling said'plurality of beams, electrode means including a tubularelectrode having a plurality of electrically connected partitionsextending longitudinally of said electrode for providing a plurality ofclosely adjacent parallel cellular passages extending therethrough andthrough which said electron beams are directed, each of said beamssubstantially filling its respective cellular passage whereby said beamsare closely adjacent each other but have no electrical effect on eachother and a second tubular electrode adjacent said first but spacedtherefrom to provide a gap and provided with a plurality of electricallyconnected partitions extending longitudinally of said electrode forproviding a plurality of closely adjacent parallel cellular passagesextending therethrough' and registering with the cellular passages inthe first tubular electrode, energy being transferred to said secondtubular electrode provided with cellular passages when said beams ofelectrons pass across the gap between the tubular electrodes.

4. An electron discharge device having means for supplying electrons,means for forming said electrons into a plurality of closely adjacentparallel beams and for simultaneously controlling said plurality ofbeams, a first tubular electrode having a plurality of electricallyconnected partitions extending longitudinally of said electrode forproviding a plurality of closely adjacent parallel cellular passagesextending therethrough through which said electron beams are directed,each of said beams substantially filling its respective cellular passagewhereby said beams are closely adjacent each other but have noelectrical effect on each other, a second tubular electrode having aplurality of electrically connected partitions extending longitudinallyof said electrode for providing a plurality of closely adjacent parallelcellular passages extending therethrough and positioned closely to saidfirst tubular electrode but separated therefrom by a small gap, thecellular passages of said second electrode registering with the cellularpassages of said first tubular electrode, energy being transferredbetween the electron beams and the second tubular electrode upon passageof the beams across the gap between the tubular electrodes, andelectrode means for collecting the electron beams after passage of thebeams past said gap.

5. 'An electron discharge device having means for supplying electrons,means for forming said electrons into a plurality of closely adjacentparallel beams, and means for simultaneously controlling said pluralityof beams for modulating said beams, a first tubular electrode having aplurality of electrically connected partitions extending longitudinallyof said electrode for providing a plurality of closely adjacent parallelcellular passages extending therethrough through which said electronbeams are directed, each of said beams substantially filling itsrespective cellular passage whereby said beams are closely adjacent eachother but have no electrical efiect on each other, a second tubularelectrode provided with a plurality of electrically connected partitionsextending longitudinally of said electrode for providing a plurality ofclosely adjacent parallel cellular passages and positioned closely tosaid first tubular electrode but separated therefrom by a smal1 gap, thecellular passage ways of said second electrode registering with thecellular passages of said first tubular electrode, energy beingtransferred between the modulated electron beams and the second tubularelectrode upon passage of the beams across the gap between the tubularelectrodes and electrode means for collecting the electron beams afterpassage of the beams past said gap.

6. An electron discharge device having a cathode for supplyingelectrons, means for directing electrons from said cathode in streams inopposite directions and for forming each of the streams into a pluralitof closely adjacent electron beams, said means being adapted to receivea controlling alternating potential for simultaneously modulating all ofsaid beams, a tubular electrode positioned on each side of said cathodeand each provided with a plurality of cellular passage ways extendingtherethrough and registering with the electron beams, a collectorelectrode surrounding the cathode, the beam forming means and thetubular electrodes and a tubular electrode positioned between each ofsaid first tubular electrodes and said collector electrode and providedwith a plurality of cellular passage ways extending therethrough andregistering with the cellular passage ways in the first tubularelectrodes.

'7. An electron discharge device having a cathode for supplyingelectrons, means for directing electrons from said cathode in streams inopposite directions and for forming each of the streams into a pluralityof closely adjacent electron beams, said means being adapted to receivea controlling alternating potential for simultaneously modulating all ofsaid beams in one stream, a tubular electrode positioned on each side ofsaid cathode and each provided with a plurality of cellular passage waysextending therethrough and registering with the electron beams, and acollector electrode for receiving the beams of electrons and surroundingsaid cathode, directing means and tubular electrode, and means forproviding a magnetic field parallel to and extending through saidtubular electrode.

8. An electron discharge device having means for supplying electrons,means for forming said electrons into a plurality of closely adjacentbeams, a plurality of electrically separated tubular electrodespositioned adjacent the beam forming means and each provided with aplurality of closely adjacent cellular passage ways extendingtherethrough and registering with the plurality of electron beams, asecond group of tubular electrodes provided with cellular passage Waysextending therethrough and registering with the passage ways in thefirst tubular electrode, said second group of tubular electrodes beingadapted to receive an alternating potential for separately modulatingthe electron beams emerging from the tubular electrode registering witheach of the second tubular electrodes, output electrodes each having aplurality of cellular passage ways therethrough registering with thepassage ways of the first and second tubular electrodes and a collectorelectrode for receiving electrons after their passage through said lasttubular electrode.

9. An electron discharge device having means for supplying electrons,means for forming said electrons into a plurality of closely adjacentbeams, a plurality of electrically separated tubular electrodespositioned adjacent the beam forming means and each provided with aplurality of closely adjacent cellular passage ways extendingtherethrough and registering with the plurality of electron beams, asecond group of tubular electrodes provided with cellular passage waysextending therethrough and registering with the passageways in the firsttubular electrode, said second group of tubular electrodes being adaptedto receive an alternating potential for separately modulating theelectron beams emerging from the tubular electrode registering with eachof the second tubular electrodes, output electrodes each having aplurality of cellular passage ways therethrough registering with thepassage ways of the first and second tubular electrodes and a collectorelectrode for receiving electrons after their passage through said lasttubular electrode, and a suppressor electrode positioned between thecollector and each of the output electrodes and comprising atubularelectrode provided with cellular-like passage ways extendingtherethrough registering with the cellularlike passage ways of saidother tubular electrodes.

10. An electron discharge device having a cathode for supplyingelectrons, means for forming said electrons into a plurality of closelyadjacent beams, a plurality of electrically separated coextensivetubular electrodes positioned adjacent the beam forming means and eachprovided with a plurality of closely adjacent cellular passage Waysextending therethrough and registering with the plurality of electronbeams, a second group of tubular electrodes provided with cellularpassage ways extending therethrough and registering with the passageways in the first tubular electrode, said second group of tubularelectrodes be ing adapted to receive an alternating potential forseparately modulating the electron beams emerging from the plurality oftubular electrodes registering with each of the second tubularelectrodes, output electrodes each having a plurality of cellularpassage ways therethrough' registering with the passage ways of thefirst and second tubular electrodes and a collector electrode forreceiving electrons after their passage through said last tubularelectrode, and a third tubular electrode positioned between each of thefirst and second tubular electrodes and provided with cellular-likepassage ways extending therethrough registering with the cellular-likepassage ways of said other tubular electrodes.

ANDREW V. HAEFF.

